1. Field of the Invention
The invention relates to power transmission mechanisms with a clutch brake for overcoming inertia during ratio changes.
2. Background Art
A typical powertrain for a road vehicle comprises an engine and a multiple-ratio power transmission together with a master disconnect clutch for establishing and disestablishing a power flow path from the engine through the transmission. Transmission ratio shifts are accomplished during a ratio shift interval in which the vehicle operator disengages the master clutch. A torque input shaft for the transmission must decelerate during a transmission ratio shift so that the relative speeds of gearing elements of the oncoming torque flow path are generally in synchronism. The time required to accomplish a ratio shift and to improve shift quality is dependent on deceleration rate of a transmission power input shaft. It is known design practice to increase the rate of deceleration by using an inertia brake for the power input shaft during a shift interval, thereby improving shift quality.
An example of a transmission input shaft inertia brake with an electromagnetic brake actuator is disclosed in U.S. Pat. No. 7,000,748. That patent is assigned to the assignee of the present invention. The brake includes an armature that frictionally engages a stationary friction surface on a transmission housing thereby retarding rotation of the transmission torque input shaft at the onset of a ratio shift.
Another example of an electromagnetic inertia brake is disclosed in U.S. patent publication 2007/0095625, which also is assigned to the assignee of the present invention. An armature hub disclosed in that publication is drivably connected to the power input shaft of the transmission, such as by a spline or keyway and key connection. An armature plate is secured to the armature hub by a flexible drive plate. When the electromagnetic coil windings are energized, the flexible drive plate allows the armature to frictionally engage a friction surface for the transmission housing. The braking capacity of the electromagnetic brake of the patent publication is determined by the friction torque developed on a single side of the armature.